Liquid discharge apparatus and method for driving liquid discharge head

Abstract

A liquid discharge apparatus comprises: a liquid discharge head that discharge a liquid by varying a volume of a pressure chamber with an actuator; a control unit that generates a drive signal that varies the volume of the pressure chamber; and an actuator driving unit that drives the actuator with the drive signal, wherein the drive signal includes a plurality of discharge pulses and a non-discharge pulse, the non-discharge pulse is applied at a time point at which a vibration velocity of a composite residual vibration that is of a liquid near a nozzle and that is generated by the discharge pulses peaks in a direction toward an inside or outside of the nozzle, the time point being synchronized with an intermediate time point between a fall time point and a rise time point of the non-discharge pulse.

What is claimed is: 
     
       1. A liquid discharge apparatus comprising:
 a liquid discharge head that discharges a liquid by varying a volume of a pressure chamber with an actuator; 
 a control unit that generates a drive signal that varies the volume of the pressure chamber; and 
 an actuator driving unit that drives the actuator with the drive signal, 
 wherein the drive signal includes a plurality of discharge pulses and a non-discharge pulse; and wherein 
 the non-discharge pulse is applied at a time point at which a vibration velocity of a composite residual vibration, including a composite of residual vibration of a liquid near a nozzle and that is generated by the discharge pulses, reaches a peak in a direction toward an inside or outside of the nozzle; the time point being synchronized with an offset time point at a middle time point between a fall time point and a rise time point of the non-discharge pulse. 
 
     
     
       2. A liquid discharge apparatus comprising:
 a liquid discharge head that discharge a liquid by varying a volume of a pressure chamber with an actuator; 
 a control unit that generates a drive signal that varies the volume of the pressure chamber; and 
 an actuator driving unit that drives the actuator with the drive signal, 
 wherein the drive signal includes a plurality of discharge pulses and a non-discharge pulse, 
 wherein the non-discharge pulse is applied at a time point at which a vibration velocity of a composite residual vibration that is of a liquid near a nozzle and that is generated by the discharge pulses peaks in a direction toward an inside or outside of the nozzle, the time point being synchronized with an intermediate time point between a fall time point and a rise time point of the non-discharge pulse, and 
 wherein the control unit includes:
 a discharge pulse interval determining unit that determines a pulse interval between the discharge pulses based on image data; 
 a composite vibration phase calculating unit that calculates a phase difference between the composite residual vibration that is of the liquid near the nozzle and that is generated by the discharge pulses, and a residual vibration that is of the liquid near the nozzle and that is generated by a first or last discharge pulse among the discharge pulses; 
 an excitation interval calculating unit that calculates an excitation interval between the last discharge pulse among the discharge pulses and the non-discharge pulse based on the pulse interval determined with the discharge pulse interval determining unit, and the phase difference calculated with the composite vibration phase calculating unit; and 
 a drive signal generating unit that generate the drive signal including the discharge pulses and the non-discharge pulse based on the pulse interval and the excitation interval. 
 
 
     
     
       3. The liquid discharge apparatus according to  claim 2 , further comprising:
 a viscosity and decay rate linking table in which the link between a viscosity and decay rate of the liquid is recorded, 
 wherein the composite vibration phase calculating unit obtains a decay rate of the residual vibration of the liquid from the viscosity and decay rate linking table to calculate the phase difference based on the obtained decay rate. 
 
     
     
       4. The liquid discharge apparatus according to  claim 2 , further comprising:
 a temperature and viscosity linking table in which a relationship between a temperature near the nozzle on the liquid discharge head and the viscosity of the liquid is recorded, 
 wherein the composite vibration phase calculating unit obtains a viscosity corresponding to the temperature of the liquid near the nozzle based on the temperature of the liquid near the nozzle from temperature and viscosity linking table to calculate the phase difference. 
 
     
     
       5. The liquid discharge apparatus according to  claim 2 , further comprising:
 an excitation interval extending unit that further extends the excitation interval calculated with the excitation interval calculating unit by a period of n (a natural number)×a natural oscillation period of the pressure chamber. 
 
     
     
       6. The liquid discharge apparatus according to  claim 2 ,
 wherein the excitation interval calculated with the excitation interval calculating unit is an interval between a rise time point of the last discharge pulse among the discharge pulses, and a time point at which the composite residual vibration that is of the liquid near the nozzle and that is generated by the discharge pulses peaks first after a rise of the last discharge pulse and in a direction toward the inside of the nozzle, or a time point after the period of n (a natural number)×a natural oscillation period of the pressure chamber has elapsed since the time point at which the composite residual vibration peaks first after the rise of the last discharge pulse and in a direction toward the inside of the nozzle. 
 
     
     
       7. The liquid discharge apparatus according to  claim 3 ,
 wherein the composite vibration phase calculating unit finds an interval β of the phase difference between the composite residual vibration that is of the liquid near the nozzle on the liquid discharge head and that is an overlap by the discharge pulses and the residual vibration that is of the liquid near the nozzle and that is generated by the first or last discharge pulse of the discharge pulses based on the decay rate, and an interval α of the phase difference of the residual vibrations of the liquid near the nozzle between the discharge pulses. 
 
     
     
       8. The liquid discharge apparatus according to  claim 4 ,
 wherein the composite vibration phase calculating unit finds an interval β of the phase difference between the composite residual vibration that is of the liquid near the nozzle on the liquid discharge head and that is an overlap by the discharge pulses and the residual vibration that is of the liquid near the nozzle and that is generated by the first or last discharge pulse of the discharge pulses based on the decay rate, and an interval α of the phase difference of the residual vibrations of the liquid near the nozzle between the discharge pulses. 
 
     
     
       9. The liquid discharge apparatus according to  claim 5 ,
 wherein the composite vibration phase calculating unit finds an interval β of the phase difference between the composite residual vibration that is of the liquid near the nozzle on the liquid discharge head and that is an overlap by the discharge pulses and the residual vibration that is of the liquid near the nozzle and that is generated by the first or last discharge pulse of the discharge pulses based on the decay rate, and an interval α of the phase difference of the residual vibrations of the liquid near the nozzle between the discharge pulses. 
 
     
     
       10. The liquid discharge apparatus according to  claim 6 ,
 wherein the composite vibration phase calculating unit finds an interval β of the phase difference between the composite residual vibration that is of the liquid near the nozzle on the liquid discharge head and that is an overlap by the discharge pulses and the residual vibration that is of the liquid near the nozzle and that is generated by the first or last discharge pulse of the discharge pulses based on the decay rate, and an interval α of the phase difference of the residual vibrations of the liquid near the nozzle between the discharge pulses. 
 
     
     
       11. The liquid discharge apparatus according to  claim 7 ,
 wherein the excitation interval calculated with the excitation interval calculating unit is a value obtained by adding an interval (α−β) of the phase difference to a period of ¾ or 5/4 of the natural oscillation period, or obtained by subtracting the interval (α−β) from the period of ¾ or 5/4 of the natural oscillation period based on the interval α of the phase difference, the interval β of the phase difference, and the natural oscillation period of the pressure chamber. 
 
     
     
       12. The liquid discharge apparatus according to  claim 8 ,
 wherein the excitation interval calculated with the excitation interval calculating unit is a value obtained by adding an interval (α−β) of the phase difference to a period of ¾ or 5/4 of the natural oscillation period, or obtained by subtracting the interval (α−β) from the period of ¾ or 5/4 of the natural oscillation period based on the interval α of the phase difference, the interval β of the phase difference, and the natural oscillation period of the pressure chamber. 
 
     
     
       13. The liquid discharge apparatus according to  claim 9 ,
 wherein the excitation interval calculated with the excitation interval calculating unit is a value obtained by adding an interval (α−β) of the phase difference to a period of ¾ or 5/4 of the natural oscillation period, or obtained by subtracting the interval (α−β) from the period of ¾ or 5/4 of the natural oscillation period based on the interval α of the phase difference, the interval β of the phase difference, and the natural oscillation period of the pressure chamber. 
 
     
     
       14. The liquid discharge apparatus according to  claim 10 ,
 wherein the excitation interval calculated with the excitation interval calculating unit is a value obtained by adding an interval (α−β) of the phase difference to a period of ¾ or 5/4 of the natural oscillation period, or obtained by subtracting the interval (α−β) from the period of ¾ or 5/4 of the natural oscillation period based on the interval α of the phase difference, the interval β of the phase difference, and the natural oscillation period of the pressure chamber. 
 
     
     
       15. The liquid discharge apparatus according to  claim 2 ,
 wherein the drive signal generating unit generates a drive signal by adding the non-discharge pulse at a time point after the excitation interval has elapsed since the rise time point of the last discharge pulse of the discharge pulses, the time point being synchronized with the intermediate time point between the fall time point and the rise time point of the non-discharge pulse. 
 
     
     
       16. The liquid discharge apparatus according to  claim 2 , further comprising:
 a pulse interval and excitation interval linking table in which the relationship among the phase difference calculated with the composite vibration phase calculating unit, the pulse interval found from the natural oscillation period of the pressure chamber, and the excitation interval is recorded based on the pulse interval determined with the discharge pulse interval determining unit. 
 
     
     
       17. A method for driving a liquid discharge head of a liquid discharge apparatus including the liquid discharge head configured to discharge a liquid by varying a volume of a pressure chamber with an actuator, a control unit configured to generate a drive signal that varies the volume of the pressure chamber, and an actuator driving unit configured to drive the actuator with the drive signal, the method comprising:
 a discharge pulse interval determining step of determining a pulse interval between a plurality of discharge pulses based on image data; 
 a composite vibration phase calculating step of calculating a phase difference between a composite residual vibration that is of an ink near a nozzle and that is generated by the discharge pulses, and a residual vibration that is of the liquid near the nozzle and that is generated by a first or last discharge pulse among the discharge pulses; 
 an excitation interval calculation step of calculating an excitation interval between the last discharge pulse of the discharge pulses and a non-discharge pulse based on the pulse interval determined in the a discharge pulse interval determining step and the phase difference calculated in the composite vibration phase calculating step; and 
 a drive signal generating step of generating the drive signal including a plurality of discharge pulses and a non-discharge pulse based on the pulse interval and the excitation interval.